CVE-2026-63119: medium-severity vulnerability in modelcontextprotocol ruby-sdk
MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.2epss 0.2%
MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This issue is fixed in version 0.23.0.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
modelcontextprotocol · ruby-sdkRelated CVEs — modelcontextprotocol ruby-sdk
In the same product, most dangerous first.
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